He got married the day *after* the IPO. They were not marital property.

If there was no prenup, Zuckerberg benefited by waiting until after the initial public offering, report the New York Daily News and Forbes. If the marriage had taken place before the IPO, his shares could have been considered marital assets. Since it took place afterward, he can argue his Facebook holdings were separate property acquired before marriage, and they weren’t marital property. He probably couldn’t make the same argument, however, about gains made after the marriage. Earnings from work are generally considered community property.

Update: The Times weighs in on the timing:

The timing of Mark Zuckerberg’s marriage to his college sweetheart, Priscilla Chan, on Saturday, just a day after he took his company public, was certainly curious. Was he looking to clarify his net worth, which, with roughly 503 million shares, now stands at about $17 billion? And if true, many observers are speculating, did that have to do with the terms of a prenuptial agreement? The Zuckerbergs are not saying.

But what is clear, according to matrimonial law experts, is that whatever Mr. Zuckerberg earned before the marriage is still solely his property afterward.